Multiplex telephony



(No Model.) 3 Sheets-Sheet 41.

s. W. HOLMANQ MULTIPLE TELEPHONE..

rra-578,992. I Patented Mmm, 1897.

(No Modem 3 Sheets- Sheet 2.

S. W, 'HMM-AN. MULTIPLE rlzlmolxmH mamma Patented Mw. 16, 1897.

Fi g. dr.

@All l/imm, W50; :715

524% @SQL/M 3 Sheets-Sheet 3. ES. W. HULMAN.

MULTIELB TELEPHONE.

(No Model.)

` atented' M NVENTD R.

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@VMM f number of 'metallic circuits,'to increase the number of suchcircuits -without adding to IO` E [shorter intermediate`circuits,orq1may obtain from two long circuits an additional'long I'S 'in everyrespect as if` they were all original v the two windings in series andyetV readily of two otherwise unequal undulatory curf constructed foruse in practicing myinvenfiltriprovements yin Multiplex Telephony, ofwhich the followingis a-specific'ation.

' UNITED STATES PATENT OFFICE.

SILAS 7.v HOLMAN, OF BOSTON, MASSACHUSETTS.

MULTIPLEX TELEPHQNY.

- 's rncrrrcarron rormingapm of Letters retenant. 578,992, dated Marchl1e,A 1897.

Applieation'iiled May 31, 1893- To all whom it may concern.: E,

` Be it known that I, SILAS W.A HOLMAN, ref siding at Boston, in thecounty ofSuEolk and Statenf- Massachusetts, have invented certain Theobject of myinvention is, with 'a given the number of wires. i By theuse of my invention I may obtain' from two long circuits an additionalseries of circuit, or from aseries of shorter circuits, I may obtain oneor more additional longercircuits.` While none' ofthe circuits, are decreased inefficiency, the longer added circuits are more eiicient thanare original circuits o f the same, length. All. of the circuits,whether'original oradded, `may be operated circuits, each withl aseparate pairof wires.

.A special feature of my invention is the use of a double-woundelectromagnetic impedance-'coil whichiis separate'from and ad-V ditionalto the transmitting and receiving in-` struments, bntwhich is hreinafter more fully described, whose peculiar usefulness ,arises in partfrom4 the fact that itl isimpermeable to telephonecurrents tending topass through permeable to telephone currents passing through the two,windings in multiple and in part from the fact that it acts as anequalizer rents passingthroughtbe two windings inl. multiple. VIn thedrawings, Figure l is a vdiagrammatic view of the double-woundelectromagnetic impedance-coil used in practicin'gmy invention. Fig.2shows an alternative methodof windingthe coil that is equallyefficientl and more convenient in construction; ',Fig. l 3 is aperspective view-of the coilas actuallyv tion. 'Fig 4F` is a diagramshowing how two telephoneLcircuits are arranged from four parallel wiresin the mannerheretofore generally in use. Fig. 5 shows two long and twoshortltelephonelcircuits contrived from the'V same four parallel wiresaccording to my Vin- `Serial No. 476,090. (N0 model.)

I vention. Fig.v 6 shows three long telephonecir'cuits contrived' fromthe same four wires accordin g tomy invention. Fig. -7 shows one addedlong telephone-circuit contrived from;

aseries of short local circuits according to my invention.

The same letters designatelike parts in the same `or dierentl figures,numerals-being added to the letters to indicate the'different`- l partsof the same kind.

ThusT represents a telephone; L, 'a line@ l wire X, adouble-woundelectromagnetic im- 4pedance'.coi1;'M, a magnetic core; w, a'wire woundupon a core, and j a junction 'between two wires. t Y. V

' In order that the invention may be fully understood, it is convenienttofirst describeV the double wound electromagnetic impe.-

dance-coil, which plays so'importanta part in practicing the invention..

Referring to Fig. 1, M isa magnetic core. wf 102 isa wire woundaroundthe core inon'e direction, (sayleft-handed,) and w3 w* a similarwire wound around the core in the opposite direction,(sayright-handed.)In^prac tice each winding should have a1 large uum` ber'of turns, sothat alone and without the other it'would present a'considerablleimpedance to a telephone-current. If it is desired thatthe ohmic `resistance of the coil shall `not be large, wire'of largesectional area' should be used. In practice, also, the core shouldconsist' of lair-annular bundle of soft-iron wiresto increase theimpedance, as shown in Fig. V3. Thebobbin maybe intwo parts forconvenience of construction. Each bobbin, however, has two separatewindings, asv shown in Fig. 1. i Thef` peculiar usefulnessof this `coilarises from theLfact that itsl self-induction 4is so'zlarge as topractically prevent the iiow of telephone-currents through the twowindings in series,v while the mutual induc-A tion of they two -windingsis such that it practicallyfannuls the eiect of the .self-induction ofthe single coils 4when a currentV tlows -equally. through thetwowindings in multithe coil does not/act asa transmitter or receiver, butasian equalizer of two otherwise unequal telephone-currents passingthrough' the two windings in multiple, tending to iu crease the lessercurrent and to decrease the greater without material loss of energy.Thus if the telephone-current passing over. the path w' 'wz weresomewhat greater than.. th'e telephone-current passing over the path'L05 w1 the eect of the coil as a whole would be to diminish thestronger current and in# crease "the weaker current until -they becomeequal. This equalizing eectof course ex? lrends within limits towhatever circuit thel windings w' 'w21 and 105 104 may be connectedwith, so that we have here an instrument capable of equalizin'gtwootherwise unequal telephonecurrents fiowin g, for instancemponf twoparallel telephone-line wires.

For convenience of. construction I may wind the twowires side by sideabout each portion .through the two windings in.- multipla-15.19;',

so that two equal currents, whether constant, intermittent, or variable,flowing through the two windings in, multiple shall exert equal andopposing magnetizing forces not only on the core as a whole, but uponeach portion of the core. In proportion as the above-desiderata areattainedy will the beneiits of this feature o f my invention berealized.

For convenience in studying the remaining diagrams -I have designatedthe above-de-v scribed doublewound electromagnetic impedance-coil bytheletter X.

Having thus described the method of construction and properties of thedouble-wound electromagnetic 'impedance-"coil, it remains to l show howI make useof it in practicing my invention.

Fig. 4 shows four parallel line-wires connected to form two m etallictelephone-circuits in the manner heretofore generally in use. The twoline-wires L' and L2 form one metallic circuit for the two telephones Tand T2,

' and the two line-wires L11 and L1 form a second metallic circuit forthe two telephones T3 and T4.

Fig. 5 shows hom-bythe use of my invention', we may contrive two longand two short telephone-circuitsfrom the same four linewires, heredesignated L5,L1, L7, and L5. i

is a double-wound electromagnetic impedancecoil,such as is abovedescribed, inserted in lines L5 and L, as shown. As this coil isimpermeable to a telephone-current tending to pass through the twowindings in series,

the lines L5 and L6 are divided by it linto two telephone-circuits T5 T5on one side and T7 TB on' the other, and an inspection of thedialgram'shows that while conversation may be carried on between T5 andT6 or'between T7 and T.S no communication is possible between 2T5 or Tontheone hand and T7 or T8 on the other. Telephone T9 is incommunication ,with telephone T1o by the line-wires L7 and L8. Let us'next see how telephone T11 is put multiple, (hence without impedance).leaves the line'wires at j5- and je, passes through X1? in multiple,through 'telephone T12, through coil X5. inmultiple, over lines- L7 andLs in multiple, through coil X1 inmultiple, back. Thecurrent from T11,arriving' at j' and jz, hasmo to itsvstarting-pointI in telephone T11.

eiect on telephone T5", because it charges the two junctions j' and4 t72to the same potential.

For the same reason `it has-no eiect on telephones T, T7, T5,'T1, andT10. Moreover, lif the lines yL5 and L5, becausey of lslight electricalinequality, should not otherwise carry equal telephone-'cu rrents awayfrom or toward junctions -j' 'and j, the coil X1-will .react on theselines to make the currents equal, in the manner above=,described. In thesame way7 coil X has anreq-ualizing eect on currents at thetwo terminalsof T6 and also on` the two f terminalsof T7, as also` coil 'X1-1equalizesthe coil X5 those of telephone T111, and coil X1 vos'potentialof the terminals of telephone T11,

those of telephone T1. In fact these various coils act together toremove any inequalitiesof potential between lines L5 and L6 or be.

tween lines L7 and LE1 which might come from slight differences ofconductivity, capacity,

insulation, or self-induction on -these linewires.

Fig. 6 is in all respects like Fig. 5, excepting that there is nointermediate station. T13 and T1'1 are in communication over lines L17and L10, T17 and T15 over lines L11 and L15, and T15 and T16 are incommunication over lines L9 and L10 as one side of the circuit and overlines L11 and L12 as the other. The added circuit T15 T111 is found inpractice to be tele-l phonically superior to either et the originalcircuits 'T13 T11 or T17 T15. This I suppose to be due .to the factsthat the resistance and greater than the capacity between eithervoriginal pair of wires.

Fig. 7 showsa long telephone-circuit T25 TA71 contrived from a 'seriesof shorter circuitsviz. T319 T and'T 21 T22 forming one branch anu T2T26, T27 T28, and T29 T30 the other branch. As in Fig. 6, the longcircuit T23 T24 is elec trially superior to an original circuit of thesame length and of course superior per mile to the shorter circuits hereshown. f

VInspecial cases -it may be desirable to employ a single conductor oreven the earth in ,place of a metallic cireuitforming on e' branch of anaddedV circuit. Thus in Fig. .5, for eX- `ample, the telephone-circuitbetween T11 and T12, which passes from T11 to T12 over the -path 'T11 X2L5 L1 in multiple', X2, T12 might be returned from T12 to T11 by asingle conductor or by ground instead of by the-pathxXf L7 L8 inmultiple, X4, in which case the'telephonecircuit T9 T10 would of coursebe dispensed with.

I claimv 1. In combination .with two original metal lictelephone-circuits, each consisting of two conductors and a telephone ateach end of each, an added metallic telephone-circuit consisting, atcach end, of a telephone, each terminal of which is connected inmultiple withl y the two conductors of .one original circuit through twowires wound equally about each portion of a magnetic core, in oppositedirections regarding currents which flow through the two windings inmultiple.

2. In combination with an original metallic telephone-circuit,consisting of two conduc'- tors and a telephone at each end, an addedtelephone-circuit' consisting, at ,eachl end, of va telephone loneterminal of"`which is connected in multiple with the two conductors ofone original circu-it through two wires wound equally about 'eachportion of a magnetic.

core inopposi'te directions regarding currents which flow through thetwo windings in multiple, while the other terminal is connected to thecorresponding telephone at the distant end by one or more conductors orby the earth.

3. In combination with two original metal lic telephone-circuits, eachconsisting of two conductors and a telephone at each end of each, twowires connecting the twoconductors of one original circuit to the twoconductors of the other Yoriginal circuit, said wires bein g woundequally about. each portion, of a magnetic core in opposite directionsregard'- 'ing currents which flow through the two wind- '.ings inmultiple.

et. In combination with two original metallic telephone-circuits, eachconsisting of two conductors and a telephone at each end of each, anadded metallic telephone-circuit consisting, at each end, ofa-telephone, each terminal ofwhich is connected in multiple withthe twoconductors of-one original circuit through the two windings of adifferentially- -wound electromagnetic coil.

5. In combination with'an original metallic telephone-circuit,consisting 'of two conduc# tors and a telephone at each end, anl addedtelephone-circuit consisting,' at each end,- of

a telephone, one terminal of whichis connected in multiple with the twoconductors of one original circuit through the two windings of adifferentially-wound electromagnetic coil, while the other terminalisconnected to the corresponding telephone at the distant end by one ormore conductors or by.

the earth. i i

G.l In combination with two original metallic telephone-circuits, eachconsisting of two conductors and a telephone ateach end of ing andtransmitting instruments connected therewith, and a differentially-woundelectromagnetic coil which has its two windings respectively connectedto the two conductors, and which acts as an equalizerof the currentsSi:v In a line for'electrical communication, the combination oftwo'conductors; receiv- 'Iiowin g in multiple therein andnot as a trans4 mitter or receiver.

In combination with two original metal lic telephone-circuits, eachconsisting of two conductors and a telephone at each end of each, anadded metallic telephone-circnit consisting, at each end, of .atelephone, each termina-l of which is'connecte'd in multiple withl thetwo conductors of one original `circuit through two-wires wound equallyabout each portion of a magnetic core., in opposite directions regardingcurrents which ow through the two windings in multiple. 10.` Incombination with an original metallic telephone-circuit, consisting oftwo conductors and a telephone 'at each end, an added telephone-circuitconsisting, atV each end, ot a telephone, one terminal of which is-connected in multiple with the two conductors of one original circuitthrough ,two 'wires wound equally Iabout each portion of a magnetic corein opposite directions regarding currents which flow through the twowindings in multiple,.while the other terminal is connected to thecorresponding telephone at the distant end by one-or 'more conductors orby theearth.

In testimony whereof Ihave signed -my' name to this specification, inthe presence of two subscribing witnesses, this 25th day of May, 1893'.

SILAS W. HOLMAN. Witnesses: WILLIAM W. JACQUES,

'.REBEN L. ROBERTS.:

